1. Field of the Invention
The present invention relates to an ultrasonic cleaning apparatus for cleaning an object to be cleaned stored in a cleaning bath by oscillating a plurality of oscillating elements.
2. Description of the Related Art
As an example of ultrasonic cleaning apparatuses for cleaning objects to be cleaned (for example, a semiconductor wafer or glass substrate) soaked in cleaning solvent in a cleaning bath using oscillations of oscillating elements, there is an ultrasonic cleaning apparatus 410 as shown in FIG. 8. FIG. 8 is a partly cross-sectional view showing a configuration of an ultrasonic cleaning apparatus in the related art. The ultrasonic cleaning apparatus 410 includes a cleaning bath 420a for storing cleaning solvent 421, and a plurality of oscillators 441, 442, and 443 are connected to a plurality of oscillating elements 431, 432, and 433 attached to an oscillating panel 420b bonded to the bottom surface of the cleaning bath 420a. Power sources 451, 452, and 453 for supplying electric power are connected to the oscillators 441, 442, and 443, respectively. In this ultrasonic cleaning apparatus 410, the oscillating elements 431, 432, and 433 are excited by the oscillators 441, 442, and 443, so that removal of fine particles attached to the object to be cleaned soaked in the cleaning solvent 421 in the cleaning bath 420a is achieved.    [Patent Document 1] Published utility model application No. H2-4688    [Patent Document 2] Published utility model application No. S61-143685
However, in the ultrasonic cleaning apparatus 410, since the oscillating elements 431, 432, and 433 are excited by operating the plurality of oscillators 441, 442, and 443 independently from each other, unevenness in sound pressure occurs among the oscillating elements 431, 432, and 433. Therefore, sufficient removal of the fine particles attached to the object to be cleaned cannot be achieved, and hence uneven cleaning is resulted.